/*
 * Copyright (C) 2007 The Guava Authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.google.common.collect;

import static com.google.common.base.Preconditions.checkNotNull;

import com.google.common.annotations.GwtCompatible;
import com.google.common.annotations.GwtIncompatible;

import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.util.Collection;
import java.util.Comparator;
import java.util.Map;
import java.util.NavigableMap;
import java.util.NavigableSet;
import java.util.SortedSet;
import java.util.TreeMap;
import java.util.TreeSet;

import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * Implementation of {@code Multimap} whose keys and values are ordered by their natural ordering or
 * by supplied comparators. In all cases, this implementation uses {@link Comparable#compareTo} or
 * {@link Comparator#compare} instead of {@link Object#equals} to determine equivalence of
 * instances.
 *
 * <p><b>Warning:</b> The comparators or comparables used must be <i>consistent with equals</i> as
 * explained by the {@link Comparable} class specification. Otherwise, the resulting multiset will
 * violate the general contract of {@link SetMultimap}, which is specified in terms of {@link
 * Object#equals}.
 *
 * <p>The collections returned by {@code keySet} and {@code asMap} iterate through the keys
 * according to the key comparator ordering or the natural ordering of the keys. Similarly, {@code
 * get}, {@code removeAll}, and {@code replaceValues} return collections that iterate through the
 * values according to the value comparator ordering or the natural ordering of the values. The
 * collections generated by {@code entries}, {@code keys}, and {@code values} iterate across the
 * keys according to the above key ordering, and for each key they iterate across the values
 * according to the value ordering.
 *
 * <p>The multimap does not store duplicate key-value pairs. Adding a new key-value pair equal to an
 * existing key-value pair has no effect.
 *
 * <p>Null keys and values are permitted (provided, of course, that the respective comparators
 * support them). All optional multimap methods are supported, and all returned views are
 * modifiable.
 *
 * <p>This class is not threadsafe when any concurrent operations update the multimap. Concurrent
 * read operations will work correctly. To allow concurrent update operations, wrap your multimap
 * with a call to {@link Multimaps#synchronizedSortedSetMultimap}.
 *
 * <p>See the Guava User Guide article on <a href=
 * "https://github.com/google/guava/wiki/NewCollectionTypesExplained#multimap"> {@code
 * Multimap}</a>.
 *
 * @author Jared Levy
 * @author Louis Wasserman
 * @since 2.0
 */
@GwtCompatible(serializable = true, emulated = true)
@ElementTypesAreNonnullByDefault
public class TreeMultimap<K extends @Nullable Object, V extends @Nullable Object>
        extends AbstractSortedKeySortedSetMultimap<K, V>
{
    private transient Comparator<? super K> keyComparator;
    private transient Comparator<? super V> valueComparator;

    /**
     * Creates an empty {@code TreeMultimap} ordered by the natural ordering of its keys and values.
     */
    public static <K extends Comparable, V extends Comparable> TreeMultimap<K, V> create()
    {
        return new TreeMultimap<>(Ordering.natural(), Ordering.natural());
    }

    /**
     * Creates an empty {@code TreeMultimap} instance using explicit comparators. Neither comparator
     * may be null; use {@link Ordering#natural()} to specify natural order.
     *
     * @param keyComparator   the comparator that determines the key ordering
     * @param valueComparator the comparator that determines the value ordering
     */
    public static <K extends @Nullable Object, V extends @Nullable Object> TreeMultimap<K, V> create(
            Comparator<? super K> keyComparator, Comparator<? super V> valueComparator)
    {
        return new TreeMultimap<>(checkNotNull(keyComparator), checkNotNull(valueComparator));
    }

    /**
     * Constructs a {@code TreeMultimap}, ordered by the natural ordering of its keys and values, with
     * the same mappings as the specified multimap.
     *
     * @param multimap the multimap whose contents are copied to this multimap
     */
    public static <K extends Comparable, V extends Comparable> TreeMultimap<K, V> create(
            Multimap<? extends K, ? extends V> multimap)
    {
        return new TreeMultimap<>(Ordering.natural(), Ordering.natural(), multimap);
    }

    TreeMultimap(Comparator<? super K> keyComparator, Comparator<? super V> valueComparator)
    {
        super(new TreeMap<K, Collection<V>>(keyComparator));
        this.keyComparator = keyComparator;
        this.valueComparator = valueComparator;
    }

    private TreeMultimap(
            Comparator<? super K> keyComparator,
            Comparator<? super V> valueComparator,
            Multimap<? extends K, ? extends V> multimap)
    {
        this(keyComparator, valueComparator);
        putAll(multimap);
    }

    @Override
    Map<K, Collection<V>> createAsMap()
    {
        return createMaybeNavigableAsMap();
    }

    /**
     * {@inheritDoc}
     *
     * <p>Creates an empty {@code TreeSet} for a collection of values for one key.
     *
     * @return a new {@code TreeSet} containing a collection of values for one key
     */
    @Override
    SortedSet<V> createCollection()
    {
        return new TreeSet<>(valueComparator);
    }

    @Override
    Collection<V> createCollection(@ParametricNullness K key)
    {
        if (key == null)
        {
            keyComparator().compare(key, key);
        }
        return super.createCollection(key);
    }

    /**
     * Returns the comparator that orders the multimap keys.
     *
     * @deprecated Use {@code ((NavigableSet<K>) multimap.keySet()).comparator()} instead.
     */
    @Deprecated
    public Comparator<? super K> keyComparator()
    {
        return keyComparator;
    }

    @Override
    public Comparator<? super V> valueComparator()
    {
        return valueComparator;
    }

    /**
     * @since 14.0 (present with return type {@code SortedSet} since 2.0)
     */
    @Override
    @GwtIncompatible // NavigableSet
    public NavigableSet<V> get(@ParametricNullness K key)
    {
        return (NavigableSet<V>) super.get(key);
    }

    /**
     * {@inheritDoc}
     *
     * <p>Because a {@code TreeMultimap} has unique sorted keys, this method returns a {@link
     * NavigableSet}, instead of the {@link java.util.Set} specified in the {@link Multimap}
     * interface.
     *
     * @since 14.0 (present with return type {@code SortedSet} since 2.0)
     */
    @Override
    public NavigableSet<K> keySet()
    {
        return (NavigableSet<K>) super.keySet();
    }

    /**
     * {@inheritDoc}
     *
     * <p>Because a {@code TreeMultimap} has unique sorted keys, this method returns a {@link
     * NavigableMap}, instead of the {@link java.util.Map} specified in the {@link Multimap}
     * interface.
     *
     * @since 14.0 (present with return type {@code SortedMap} since 2.0)
     */
    @Override
    public NavigableMap<K, Collection<V>> asMap()
    {
        return (NavigableMap<K, Collection<V>>) super.asMap();
    }

    /**
     * @serialData key comparator, value comparator, number of distinct keys, and then for each
     * distinct key: the key, number of values for that key, and key values
     */
    @GwtIncompatible // java.io.ObjectOutputStream
    private void writeObject(ObjectOutputStream stream) throws IOException
    {
        stream.defaultWriteObject();
        stream.writeObject(keyComparator());
        stream.writeObject(valueComparator());
        Serialization.writeMultimap(this, stream);
    }

    @GwtIncompatible // java.io.ObjectInputStream
    @SuppressWarnings("unchecked") // reading data stored by writeObject
    private void readObject(ObjectInputStream stream) throws IOException, ClassNotFoundException
    {
        stream.defaultReadObject();
        keyComparator = checkNotNull((Comparator<? super K>) stream.readObject());
        valueComparator = checkNotNull((Comparator<? super V>) stream.readObject());
        setMap(new TreeMap<K, Collection<V>>(keyComparator));
        Serialization.populateMultimap(this, stream);
    }

    @GwtIncompatible // not needed in emulated source
    private static final long serialVersionUID = 0;
}
